This disclosure relates generally to the field of optics. More particularly, this disclosure relates to a novel and highly beneficial techniques for fashioning an optical stack or camera module.
Camera modules for mobile telephone and other small form-factor electronic devices are one of the key components in controlling device thickness. Referring to FIG. 1, a prior art mobile telephone handset's rear-facing camera module 100 is typically mounted between the unit's back-plate 105 (including surface-flush cover glass 110) and front cover 115; using the maximum space within the device's housing, thereby controlling the device's overall thickness. Camera module 100 also includes front or first lens 120 and, typically, one or more additional lenses (not shown) housed within lens barrel 125. Lens barrel 125, in turn, is moved toward and away from cover glass 110 by actuator mechanism 130 so as to focus incoming light through infrared cutoff filter (IRCF) 135 and onto the surface of sensor array 140. In practice, cover glass 110 is spaced at a sufficient distance from lens barrel 125 (i.e., the top of lens 120) such that when barrel 125 travels from its infinity position (furthest from glass plate 110) to its macro position (closest to glass plate 110) there is no contact between the two surfaces.
Thickness 145 of camera module 100 is controlled by several factors, a primary consideration among which is the module's overall optical track 150, defined as the distance from the camera's optical sensor surface 140 to the outer surface or top of its first lens element 120. This latter distance is fixed by the limits of Maxwell's equations (for a given sensor and pixel size). It would be beneficial to provide a means to reduce the overall camera height or thickness 145 so as to permit the design of thinner products, resulting in lower mass and improved product aesthetics.